The Saber and Scroll
of data generated by the ROUNDUP effort . Most telling among this information were the lessons learned from the Dieppe raid of August 1942 . Dieppe demonstrated that , in light of modern weapons and fortifications , a seaborne attack on an enemy-held port was not feasible . Also , the ongoing fortification of the Northwestern European coast would deny the Allies any opportunity to land unopposed and move on an enemy port . It became quite clear that any invasion of Northwest Europe would have to be an amphibious attack against a defended coastline . Such an attack could only be carried out by the use of specialized landing craft .
The primary lesson gleaned from Dieppe , however , was that the German defenses were more formidable than previously thought . Earlier iterations of ROUNDUP had called for widely dispersed landing sites to prevent the enemy from concentrating and to create confusion as to the location of the main effort . Upon examination of Dieppe , Allied planners determined that any landing force would have to be concentrated and mutually supporting in order to crack the German defenses and withstand the inevitable counterattack . A concentrated front also eased logistical concerns and allowed the invaders to reinforce the landing quickly and with greater depth . 22
The new approach called for numerous conditions necessary for success , such as suitable beach gradients , exits , tides , shelter from the prevailing winds , and access to nearby port facilities to be taken after the landings . By early 1943 the planners had determined that the Caen sector of the Normandy coast was the best , indeed the only , choice for such an operation . Secondary landings were planned for the east coast of the Cotentin Peninsula to provide access to the port of Cherbourg . On 1 March the new analysis was approved and code-named SKYSCRAPER .
SKYSCRAPER was deliberately ambitious , calling for no less than ten assault divisions afloat , four in the first wave and six in the immediate follow-up , supported by four airborne divisions dropped to block enemy reinforcements . All ten amphibious divisions were to land on the first four tides , that is , before the end of D plus 1 . The stated reason for such a bold enunciation was to bring to light the problems inherent in such an operation so they could be planned for and dealt with . It did not disappoint in this regard . 23
Although the Combined Chiefs of Staff approved SKYSCRAPER as a basis for planning , immediate questions arose as to its methodology . The British Chiefs challenged the planners ' assertion that SKYSCRAPER ' S force allocation was the bare minimum required for the operation given the justification that they expected " determined opposition " from the Germans . The Chiefs pointed out the impossibility of basing an operation on projected enemy strength over a year in the future .
The SKYSCRAPER planners countered that a firm decision must be made to ensure that the resources needed to accomplish the mission would be made available . Refusing to do so , they believed , opened the door to
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